What is the role of fibrinogen in managing a snake bite?

Role of Fibrinogen in Snake Bite Management

Fibrinogen plays a critical role in snake bite management as it is often the first coagulation factor to be depleted, leading to coagulopathy and potentially life-threatening bleeding. Monitoring and replacing fibrinogen is essential for preventing morbidity and mortality in snake bite victims.

Pathophysiology of Fibrinogen in Snake Bites

• Fibrinogen is the final component in the coagulation cascade and serves as the ligand for platelet aggregation, making it key to effective coagulation and platelet function 1
• Snake venoms, particularly from vipers, contain:
  • Prothrombin activators that rapidly consume fibrinogen
  • Thrombin-like enzymes that directly cleave fibrinogen
  • Fibrinogenolytic components that directly degrade fibrinogen 2, 3, 4
• This leads to Venom-Induced Consumption Coagulopathy (VICC), characterized by:
  • Severe hypofibrinogenemia or afibrinogenemia
  • Coagulation dysfunction
  • Persistent bleeding 5

Clinical Manifestations of Fibrinogen Depletion

• Persistent bleeding from puncture sites and venous access
• Subcutaneous hemorrhage
• Incoagulable blood
• Elevated fibrin degradation products
• Abnormal thromboelastography findings 5, 2

Monitoring Fibrinogen Levels

1. Laboratory Assessment:

   • Clauss fibrinogen assay (standard method)
   • Target: Maintain fibrinogen levels >1.5-2.0 g/L 1

2. Viscoelastic Testing (preferred):

   • Thromboelastometry (ROTEM) or Thromboelastography (TEG)
   • FIBTEM/Functional Fibrinogen Assay provides rapid assessment of fibrinogen function
   • Maximum Clot Firmness (MCF) <7 mm correlates with fibrinogen level of approximately 2 g/L
   • Viscoelastic methods are preferable due to faster results and better assessment of functional fibrinogen 1, 6

Fibrinogen Replacement Therapy

For snake bite victims with evidence of hypofibrinogenemia or functional fibrinogen deficit:

1. Indications for replacement:

   • Significant bleeding with thromboelastometric signs of fibrinogen deficit
   • Plasma fibrinogen level <1.5-2.0 g/L
   • Maximum Clot Firmness in FIBTEM ≤4-6 mm 1

2. Replacement options:

   • Fibrinogen concentrate: Initial dose 3-4 g
   • Cryoprecipitate: 50 mg/kg (approximately 15-20 single donor units in a 70 kg adult) 1, 6

3. Monitoring after replacement:

   • Repeat fibrinogen levels or viscoelastic testing
   • Target physiological levels (>1.5-2.0 g/L or >9 mm MCF in FIBTEM)
   • Avoid targeting supranormal levels (>14 mm MCF in FIBTEM) 1, 6

Special Considerations

• Persistent fibrinogen deficiency may occur in some snake bites even after initial treatment, requiring repeated fibrinogen replacement 5
• Antivenom administration is crucial as it helps eliminate venom components from circulation, but may not directly reverse fibrinogenolytic effects already present 3
• Monitor for potential anaphylactic reactions to antivenom 3
• Some snake venoms (e.g., Bothrops species) trigger inflammatory responses that interact with coagulation pathways, affecting fibrinogen consumption 7

Treatment Algorithm

1. Assess for coagulopathy (bleeding, laboratory tests, viscoelastic testing)
2. Administer specific antivenom as soon as possible
3. Monitor fibrinogen levels or viscoelastic parameters
4. Replace fibrinogen if levels fall below 1.5-2.0 g/L or FIBTEM MCF ≤6 mm
5. Continue monitoring and replace as needed until coagulopathy resolves
6. Follow up until complete normalization of coagulation parameters (may take up to 25 days in severe cases) 5

By understanding and addressing the critical role of fibrinogen in snake bite management, clinicians can significantly reduce morbidity and mortality associated with venom-induced coagulopathy.